| 摘要 |
PURPOSE: To form a Cr oxide film and to obtain excellent surface characteristic, corrosion resistance, and toughness by adding prescribed amounts of Cr and Cu to a composition and controlling rolling and also controlling cooling conditions after rolling. CONSTITUTION: This gauge H steel has a composition containing, by weight ratio, 0.05-0.15% C, 0.05-0.50% Si, 0.8-2.0% Mn, 0.003-0.015% N, <=0.005% Al, 0.50-1.50% Cr, and 0.30-1.00% Cu and further containing, if necessary, <=1% N, and further, a Cr oxide film is formed between the base material of this shape steel and a scale and also the thickness of this scale is regulated to <=10μm. At the time of rolling of this shape steel, a continuously cast bloom is reheated to 1100-1300 deg.C for 1-<3hr and then rolling is started, and finish rolling is finished at 750-1050 deg.C. Then, accelerated cooling is done without delay from 700 to 400 deg.C at (0.5 to 10.0) deg.C/s average cooling rate. It is preferable to apply water cooling to the surface layer part of the steel stock in the intermediate stage of rolling and also to apply rolling at least once or more in the course of recuperation.
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